Electrical stimulation for treating neurological disorders

ABSTRACT

A method for treating a disorder of a patient. The method comprises transcutaneously delivering electrical energy to a targeted tissue site at a frequency of at least 50 KHz, thereby treating the disorder.

RELATED APPLICATION DATA

The present application is a continuation of U.S. application Ser. No.15/003,092, filed Jan. 21, 2016, which is a continuation of U.S.application Ser. No. 14/312,066, filed Jun. 23, 2014, now issued as U.S.Pat. No. 9,242,085, which claims the benefit under 35 U.S.C. §119 toU.S. Provisional Patent Application No. 61/841,199, filed Jun. 28, 2013.The foregoing applications are hereby incorporated by reference into thepresent application in their entirety.

TECHNICAL FIELD

The present disclosure relates to systems and methods fortranscutaneously treating neurological disorders in patients.

BACKGROUND OF THE INVENTION

Transcutaneous electrical nerve stimulation (TENS) is a knownnon-invasive technique extensively used by numerous health-careproviders worldwide. TENS uses an electrical current to stimulate nervesand acupuncture points across the surface of the skin. Due to itssimplicity, TENS can be administered either in clinics by health-careprofessionals or at home by patients through various TENS devicesavailable in the market. Its ease of use, general safety and portabilitymake it a preferred treatment over a long term use of medications andnerve blocks for chronic pain.

A variety of TENS techniques which differ in terms of specificmodalities of treatment are known. Few examples of these techniquesinclude acupuncture-like TENS (ALTENS) and Intense TENS, which aretypically applied to stimulate nerves for pain relief. These modalitiesare characterized based on various parameters, such as pulse frequency,pulse amplitude, pulse duration, analgesic effects, pulse pattern, etc.

Although TENS techniques are generally successful for non-invasivelystimulating nerves within a patient's body, due to the relatively highimpedance of the skin and underlying tissue, TENS techniques are limitedto stimulating nerves near the surface of the skin. In order to overcomethe high impedance of the tissue, the amplitude of the electric currentcan be theoretically increased to treat nerves that are deeper in thebody. However, such an increase in amplitude may cause tissue heating,and thus, pain to the patient.

It may therefore be beneficial to provide methods to provide orotherwise enable such treatments, but which are non-invasive, reducetissue heating and yield intended therapeutic effect(s) for treatment ofdisorders of the patient.

SUMMARY OF THE INVENTION

In accordance with the present inventions, a method for treating adisorder of a patient is provided. The disorder may be, e.g., asthma,skin cancer, alopecia, irritable bowel syndrome, inflammatory boweldisease, diabetes, multiple sclerosis, amyotrophic lateral sclerosis(ALS), high cholesterol, overactive bladder, migraine, headache,fibromyalgia, complex region pain syndrome (I and II), angina,arthritis, leprosy, or chronic pain. The method comprisestranscutaneously delivering electrical energy (e.g., an electrical pulsetrain) to a targeted tissue site at a frequency of at least 50 KHz, andperhaps at least 100 KHz, thereby treating the disorder. The targettissue site may be at least 2 cm, but perhaps not more than 4 cm,beneath the skin of the patient. The stimulation energy may be appliedby a patch electrode affixed to the skin of the patient.

Other and further aspects and features of the invention will be evidentfrom reading the following detailed description of the preferredembodiments, which are intended to illustrate, not limit, the invention.

BRIEF DESCRIPTION OF DRAWINGS

The drawings illustrate some embodiments of the present disclosure, inwhich similar elements are referred to by common reference numerals. Inorder to better appreciate how the above-disclosed and other advantagesand objects of the present disclosure are obtained; a more particulardescription of the present disclosure briefly described above will berendered by reference to specific embodiments thereof, which areillustrated in the accompanying drawings. Understanding that thesedrawings depict only typical embodiments of the disclosure and are nottherefore to be considered limiting of its scope, the disclosure will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings in which:

FIG. 1 is a plan view of an exemplary transcutaneous neurostimulationsystem, according to an embodiment of the present disclosure;

FIG. 2 is a plan view that illustrates an exemplary placement ofelectrodes of the neurostimulation system of FIG. 1 for treatment ofasthma, according to an embodiment of the present disclosure; and

FIG. 3 is a plan view that illustrates an exemplary placement ofelectrodes of the neurostimulation system of FIG. 1 for treatment ofarthritis, according to another embodiment of the present disclosure.

DETAILED DESCRIPTION

Turning first to FIG. 1, an exemplary transcutaneous neurostimulationsystem 10 will be described. The system 10 includes patch electrodes12-1 and 12-2 (collectively, electrodes 12) and a neurostimulator 14.The patch electrodes 12 may store an electrically conducting medium,such as various known, related art and/or later developed hydrophilicmaterials and hydrogels, and configured to release the medium from aside that is to be placed in communication with a patient's skin.Alternatively, this electrically conductive medium may be appliedseparately between the electrodes 12 and the skin.

The neurostimulator 14 generally includes a stimulation output circuit16, a monitoring circuit 18, a controller/processor 20, and a powersource 22. The stimulation output circuit 16 is configured to generateelectrical stimulation energy in accordance with a relatively high rateelectrical pulse train to treat a disorder. Alternatively, a relativelyhigh frequency continuous stimulation waveform, e.g., sinusoidalwaveform, may be generated by the stimulation output circuit 16 in amanner as disclosed in U.S. Provisional Patent Application Ser. No.61/646,773, entitled “System and Method for Shaped Phased CurrentDelivery,” which is expressly incorporated herein by reference in itsentirety.

The pulse rate of the electrical pulse train may be controlled eitheralone or in any combination with a set of other stimulation parameters.Exemplary stimulation parameters include, but are not limited to,electrode combinations, which define the electrodes that are activatedas anodes (positive), cathodes (negative), and turned off (zero), andpercentage of stimulation energy assigned to each electrode 12 of thearray of electrodes (fractionalized electrode configurations), andelectrical pulse parameters, which define pulse width (measured inmicroseconds), and/or burst rate (measured as the stimulation ONduration X and stimulation OFF duration Y).

The stimulation output circuit 16 may include a variety of architecturesfor delivering electrical stimulation energy. In one example, thestimulation output circuit 16 may include independently controlledcurrent sources for providing stimulation pulses of specified and knownamperage to or from the electrodes 12. In another example, the outputcircuit 16 may include independently controlled voltage sources forproviding stimulation pulses of a specified and known voltage at theelectrodes 12 or to multiplexed current or voltage sources that are thenconnected to the electrodes 12. The operation of this stimulation outputcircuit 16, including alternative embodiments of suitable outputcircuit(s) for performing the same or similar function of generatingstimulation pulses of a prescribed amplitude and width, is disclosedmore fully in U.S. Pat. Nos. 6,516,227 and 6,993,384, which areexpressly incorporated herein by reference in their entireties. Theelectrical stimulation energy generated by the stimulation outputcircuit 16 is output to the electrodes 12.

The monitoring circuit 18 is configured to monitor the status of variousnodes or other points throughout the system 10, e.g., power supplyvoltages, temperature, battery voltage, etc. In some embodiments, themonitoring circuit 18 may monitor changes in various physiologicalparameters at and/or around the stimulation area adjacent to theelectrodes 12 by using the electrodes 12 as sensors or a separate sensor(not shown) located in the patient's body. Exemplary physiologicalparameters include, but are not limited to, blood pressure, acidicconcentration, and/or temperature.

The controller/processor 20 is configured for obtaining status data fromthe monitoring circuit 18 and controlling the stimulation output circuit16 to output the stimulation energy in accordance with the stimulationparameters. In the illustrated embodiment, the controller/processor 20manages the neurostimulation therapy based on a user input receivedthrough a user interface (not shown) of the neurostimulation system 10.Alternatively or additionally, the controller/processor 20 may beconfigured for managing the neurostimulation therapy based on changes inthe physiological parameters sensed at or around the electrodes 12 andmonitored by the monitoring circuit 18.

The power source 22 includes a mains power supply for powering theneurostimulator 14. The power source 22 generates various voltages, someof which are regulated and some of which are not, as needed by thevarious circuits located within the system 10. The system 10 may receivethe control and status signals from the controller/processor 20, andaccordingly generate electrical stimulation energy, which is deliveredtranscutaneously to a target tissue site, or to a target nerve, fortreating a disorder.

During operation, the patch electrodes 12 are affixed to the skin at alocation adjacent to a target tissue, or target nerve, for treating thedisorder. Electrical stimulation energy is delivered to the electrodes12 from the stimulation output circuit 16 to transcutaneously stimulatethe target nerve. This type of transcutaneous electrical stimulation ofthe target nerve may induce pain or become relatively uncomfortable forthe patient. In order to improve or otherwise enhance the patient'stherapy experience, anesthesia may be applied on the skin at the area ofstimulation on the skin. At and/or around the stimulation area adjacentto the electrodes 12, the patient's skin may be coated with a variety ofknown, related art or later developed analgesic, prophylactic and/orcurative gels or pastes, before and/or after delivering the electricalstimulation energy to the electrodes 12. This procedure may reduce oreven avoid skin damage and/or minimize, or avoid pain experienced by thepatient.

Electrical energy will be delivered between the electrodes 12, so thatthe electrical current has a path from the stimulation output circuit 16to the target nerve and a sink path from the target nerve to thestimulation output circuit 16. Electrical energy may be transmitted tothe target nerve in a monopolar or a bipolar fashion, or by any othermanner available depending on the available number of electrodes foroperation.

Monopolar delivery occurs when a selected electrode, such as the patchelectrode 12-1, is activated along with the other patch electrode, suchas the electrode 12-2, behaving as a ground electrode so that electricalenergy is transmitted between the selected electrode 12-1 and the groundelectrode 12-2. The selected electrode 12-1 is placed transcutaneouslyadjacent to the target nerve, for e.g., vagus nerve, and the groundelectrode 12-2 is placed on the body far away from the target nerve. Fore.g., the ground electrode 12-2 may be placed transcutaneously aroundabdomen or leg of the patient. Monopolar delivery may also occur whenone or more of the electrodes 12 are activated along with a large groupof lead electrodes (not shown) located remotely from the electrode(s) 12so as to create a monopolar effect; that is, electrical energy deliveredby the stimulation output circuit 16 is conveyed from the electrode(s)12 in a relatively isotropic manner. Bipolar delivery occurs when two ofthe electrodes 12-1 and 12-2 are activated as anode and cathoderespectively, so that electrical energy is transmitted between theelectrodes 12. In this case, both the electrodes 12 are located adjacentto the target nerve.

Significantly, the stimulation output circuit 16 delivers the electricalstimulation energy at a substantially high frequency of at least 50 KHzor more, such as 100 KHz, to stimulation the target nerve, which may belocated 2 cm or more, such as 4 cm, beneath the skin. The high frequencyof the electrical stimulation energy reduces impedance of the skin,thereby decreasing the amplitude of current needed to penetrate the skinand underlying tissue to reach the target nerve, and preventing heatingor damage to the skin and underlying tissue. While the stimulationoutput circuit 16 delivers the electrical stimulation energy to theelectrodes 12, the monitoring circuit 18 optionally monitors inducedchanges in the physiological parameters at and/or around the stimulationarea adjacent to the electrodes 12. If any of the physiologicalparameters, such as blood pressure, acidic concentration, and/or heat,at or around the stimulation area exceed their respective thresholdvalues, then the controller/processor 20 may automatically deactivatethe stimulation output circuit 16, which stops the delivery ofelectrical stimulation energy to the electrodes 12. Alternatively, thestimulation output circuit 16 may be deactivated through a user input(manually) in response to perceived pain by the patient.

The transcutaneous stimulation system 10 may be used to treat a varietyof disorders. In one example, the system 10 is used to treat asthma bystimulating the vagus nerve 202, as shown in FIG. 2. The vagus nerve 202is a parasympathetic nerve, which includes both motor and sensory fibersand passes from the brain 204 through the neck and thorax to theabdomen. The vagus nerve 202 descends behind the root of the lungs (notshown), where the nerve 202 spreads out to form posterior pulmonaryplexus, whose branches accompany the ramifications of the bronchithrough the lung tissue. If the patient is suffering from asthma, thevagus nerve 202 is hypersensitive to external stimuli, such as dust,smoke, and pollen, which cause the airway to narrow and produce excessmucus, leading to the patient experiencing difficulty in breathing.Electrical stimulation energy may therefore be applied to the vagusnerve 202 to provide a therapeutic effect relative to asthma and reduceconstriction of the airway.

The electrodes 12 are placed near, adjacent and/or around a patient'sear, to reduce the possibility of accidently or unintentionallystimulating other nerves, such as phrenic nerve controlling respiration.Specifically, the electrodes 12 can be affixed to the skin in order totranscutaneously stimulate the vagus nerve 202, which is relativelydeeper from the skin at a location near or around the ear.

During operation, once the electrodes 12 are positioned over the skinadjacent to the vagus nerve 202, the stimulation output circuit 16 maybe activated to apply the electrical stimulation energy to theelectrodes 12. As disclosed above, this electrical stimulation energy isof a substantially high frequency for transcutaneously stimulating thevagus nerve 202.

As mentioned above, this high frequency allows the electricalstimulation energy to reduce the impedance of the skin and penetratedeeper within the body. In fact, the electrical stimulation energy isable to reach the vagus nerve 202 without significant heating of theskin and underlying tissue. Further, the high frequency of theelectrical stimulation therapy prevents the need of increasing the pulseamplitude of the electrical stimulation energy to reach a target tissue,such as the vagus nerve 202. As a result, relatively less charge(current amplitude x pulse width) or charge density (charge per unitarea of the tissue) is transferred to the target tissue such as thevagus nerve 202 during therapy and thus minimizes tissue heating. Theelectrical stimulation energy may also have a low duty cycle so that thecharge or charge injected per second (current amplitude x pulse width xrate (or period)) is reduced to enable a relatively safer therapeuticregime.

The frequency of the electrical stimulation energy may be selected basedon the depth of the vagus nerve 202. For example, if the depth of thevagus nerve 202 is 2 cm beneath the skin at a location around the ear ofthe patient, the frequency of the electrical stimulation energy may beset at a lower frequency (e.g., 50 KHz). If the depth of the vagus nerve202 is 4 cm beneath the skin at a location around the ear of thepatient, the frequency of the electrical stimulation energy may be setat a higher frequency (e.g., 100 KHz). Thus, in general, the greater thedepth of the vagus nerve 202, the greater the frequency of the appliedelectrical stimulation energy should be.

Upon perception of pain during treatment of the disorder, in response touser input, the amplitude of applied electrical stimulation energy maybe reduced by the stimulation output circuit 16 to prevent tissueheating, and the frequency of the applied electrical stimulation energymay be increased by the stimulation output circuit 16 to reduce thetissue impedance, so that the decreased electrical stimulation energyreaches the vagus nerve 202. Similarly, the stimulation output circuit16 may automatically reduce the amplitude and increase the frequency ofthe applied electrical stimulation energy if the controller/processor 20determines that a physiological parameter at or around the stimulationarea has exceeded a predetermined threshold value to avoid the patientfrom experiencing pain during therapy. The electrical stimulation energymay be applied to the electrodes 12 multiple times at regular intervals,or alternatively spread across multiple sessions for a predefined periodof time.

In another example shown in FIG. 3, the system 10 may be used fortreating arthritis in a patient's knee by stimulating nerves, such asthe common peroneal nerve 302 and saphenous nerve 304. The patchelectrodes 12 may be affixed to the skin over the knee, and providedwith electrical stimulation energy at a substantially high frequency. Asdiscussed above with respect to the vagus nerve, the frequency of theapplied electrical stimulation can be set based on the depth of thenerves 302, 304. Furthermore, in the case where the patient experiencespain, the amplitude of the applied electrical stimulation energy may bereduced and the frequency of the applied electrical stimulation energymay be increased, as discussed above with respect to FIG. 2. Also, theelectrical stimulation energy may be applied to the electrodes 12multiple times at regular intervals, or alternatively spread acrossmultiple sessions for a predefined period of time, as described abovewith respect to FIG. 2, in order to treat arthritis.

In addition to the above methods, various neurological disorders may betreated by the disclosed transcutaneous stimulation of target tissue ata substantially high frequency. Examples of these neurological disordersinclude, but are not limited to, skin cancer, alopecia, irritable bowelsyndrome, inflammatory bowel disease, diabetes, multiple sclerosis,amyotrophic lateral sclerosis (ALS), high cholesterol, overactivebladder, migraine, headache, fibromyalgia, complex region pain syndrome(I and II), angina, arthritis, leprosy, and/or chronic pain.

Although particular embodiments of the present disclosure have beenshown and described, it will be understood that it is not intended aslimiting to the disclosed embodiments, and it will be obvious to thoseskilled in the art that various changes and modifications may be madewithout departing from the spirit and scope of the present inventions.Thus, the various embodiments are intended to cover alternatives,modifications, and equivalents, which may be included within the spiritand scope of the present inventions as defined by the claims.

What is claimed is:
 1. A method, comprising: selecting a frequency ofelectrical stimulation energy for treating a disorder of a patient, thefrequency selection being based on a distance to be traveled by theelectrical stimulation energy through tissue to a neural target;selecting an amplitude of the electrical stimulation energy, theamplitude selection being based on the selected frequency and based on alimit of charge injection into the tissue; and providing instructions toa neural stimulator to stimulate the neural target using the selectedfrequency and the selected amplitude.
 2. The method of claim 1, whereinthe frequency is at least 50 KHz.
 3. The method of claim 1, wherein theneural tissue includes a peripheral nerve.
 4. The method of claim 1,wherein the neural tissue includes motor fibers.
 5. The method of claim1, wherein the neural target is between 2 cm and 4 cm beneath skin. 6.The method of claim 1, further comprising receiving a signal indicativeof patient-perceived pain, increasing the frequency in response toreceiving the signal indicative of patient-perceived pain, and reducingthe amplitude based on the increased frequency and based on the limit ofcharge injection into the tissue.
 7. The method of claim 1, wherein theselecting the amplitude of the electrical stimulation energy includesselecting the amplitude based on the limit of charge density of theelectrical stimulation energy transferred into the tissue.
 8. The methodof claim 1, further comprising selecting a duty cycle based on the limitof charge injection into the tissue using the electrical stimulationenergy at the selected frequency and the selected amplitude.
 9. Amethod, comprising: controlling an impedance of tissue through whichelectrical stimulation energy is to travel through a patient, whereinthe controlling the impedance includes selecting a frequency of theelectrical stimulation energy, the frequency selection being based on adistance to be traveled by the electrical stimulation energy throughtissue to a neural target; selecting an amplitude of the electricalstimulation energy, the amplitude selection being based on the selectedfrequency and based on a limit of charge injection into the tissue; andproviding instructions to a neural stimulator to stimulate the neuraltarget using the selected frequency and the selected amplitude.
 10. Themethod of claim 9, wherein the neural target is between 2 cm and 4 cmbeneath skin.
 11. The method of claim 9, further comprising receiving asignal indicative of patient-perceived pain, increasing the frequency inresponse to receiving the signal indicative of patient perceived pain,and reducing the amplitude based on the increased frequency and based onthe limit of charge injection into the tissue.
 12. The method of claim9, wherein the selecting the amplitude of the electrical stimulationenergy includes selecting the amplitude based on the limit of chargedensity of the electrical stimulation energy transferred into thetissue.
 13. The method of claim 9, further comprising selecting a dutycycle based on the limit of charge injection into the tissue using theelectrical stimulation energy at the selected frequency and the selectedamplitude.
 14. The method of claim 9, wherein the controlling impedanceincludes reducing side effects of the electrical stimulation energy. 15.The method of claim 14, further comprising monitoring for side effectsof the electrical stimulation energy.
 16. The method of claim 15,wherein monitoring for side effects includes monitoring for an inducedchange in at least one of blood pressure, acidic concentration, or heat.17. The method of claim 14, wherein reducing side effects includesreducing tissue heating.
 18. The method of claim 9, wherein selectingthe frequency based on the distance includes increasing frequency forincreasing distances.
 19. A system, comprising: a neural stimulatorconfigured to deliver electrical energy to neural tissue at an amplitudeand at a frequency to treat a disorder of a patient; and acontroller/processor configured to: control impedance of tissue throughwhich electrical stimulation energy is to travel through a patient,including select a frequency of the electrical stimulation energy, thefrequency selection being based on a distance to be traveled by theelectrical stimulation energy through tissue to a neural target; selectan amplitude of the electrical stimulation energy, the amplitudeselection being based on the selected frequency and based on a limit ofcharge injection into the tissue; and provide instructions to a neuralstimulator to stimulate the neural target using the selected frequencyand the selected amplitude
 20. The system of claim 19, furthercomprising patch electrodes operably connected to the stimulation outputcircuit to deliver transcutaneous stimulation of the neural tissue totreat the disorder.